Conventionally, an inverter is applied to an electric motor, a vacuum cleaner, an air-conditioner, a welding machine and so forth as the power conversion apparatus. The semiconductor device in which the first semiconductor element and second semiconductor element are connected in series is used in the inverter and a power factor improvement circuit, a brake circuit and so forth which are peripheral circuits thereof.
In the inverter that a plurality of lines of the series-connected first semiconductor element and second semiconductor elements are connected in parallel, in general, it is intended to use switching semiconductor elements of the same kind such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), an IGBT (Insulated Gate Bipolar Transistor) and so forth as the first semiconductor elements which constitute an upper arm and the second semiconductor elements which constitute a lower arm.
Then, for example, in an inverter control circuit used in the vacuum cleaner, as a lower-arm-side switching element which constitutes the inverter control circuit, a switching element (for example, a wide band gap semiconductor element which uses gallium nitride (GaN), silicon carbide (SiC), diamond and so forth) which makes switching of a speed which is higher than that of an upper-arm-side switching element (for example, the IGBT) possible is applied (for example, see Patent Literature 1). In this Patent Literature 1, inverter control of a two-phase modulation system which is so made as to turn the upper-arm switching element on and turn the lower-arm switching element off in turn at intervals of 2π/3 at each phase voltage of three phase voltages to be applied to the motor thereby to periodically fix each phase voltage is performed.